I am looking to buy an other 80s cutlass . i found 1 but the lady says it runs an drives good but when you go over 45mph the engine light turns on? Any ideas?

 

You have an intermittent problem with the emissions controls. I've had a similar problem with my 86. It turned out to be low coolant level. At high engine speeds the temp sensor for the ECM became uncovered, leading to the intermittent Check Engine light. I filled the cooling system and the problem stopped.

 

GM Type I ECM codes are easy to read. All you do is short the A and B terminal in the ALDL and count flashes of the check engine light. You can cross check the codes in a Chilton's guide or at the parts store.

 

It could even be the vehicle speed sensor.

And like Olds64 said, checking the codes on the spot are easy.
Find out the code and report back to us.
The fix on those should not be hard.
If it runs and drives good, and looks good, then i would probably get it.

 

If the light comes on then goes off, there will not be a stored code to read.

 

will do asap thanx!!!!!!!!!!!!!!!!!!!!

 

i know this is like a year late but my 1984 oldsmobile delta 88 307 v8 did the same thing if i was abov 45 mph for over 5 mins the check engine light came on. well its a simple problem to fix. first jump the A and B terminal on the ALDL. and if you get 4 flashes pause 4 flashes like i did replace the oxygen sensor and itll be good as new. i garentee it was problem the o2 senser. cause mine was the same. pick up a haynes repair manual it has a list of the codes